A pavement breaker is a type of hammer drill which operates in a hammer only mode. However, other types of hammer drill operate in two modes, namely a hammer only mode or a hammer and drill mode, or in three modes of operation, namely a hammer only mode, a hammer and drill mode or a drill only mode.
EP1872913 discloses an example of a pavement breaker which comprises a cylinder in which is mounted a piston which is reciprocatingly driven by a motor via a hammer mechanism. The piston in turn reciprocatingly drives a ram which imparts impacts onto a cutting tool via a beat piece. The cylinder comprises a single bleed hole to refresh the air spring. The characteristics of the performance of the pavement breaker vary depending on the hardness of the material being cut. The problem with this design is that the characteristics of the performance of the hammer can not be adjusted.